Electric motor



0. C. MARTIN ELECTRIC MOTOR Sept. 29, 1931.

Filed April 28, 1930 2 Sheets-Sheet l INVENTGR BY 0'75 C. Mai/"2W7 MWQ WQWZQ ATTORNEYS Sept. 29, 1931 0, c, MARTIN 1,824,909

ELECTRIC MOTOR Filed April 28, 1930 2 Sheets-Sheet 2 'INVENTOR ATTOR N EYS Patented Sept. 29, 1931 emer e MWEES :PA'BENT QFFICE c mmc. on winners-figment;

YWmmera-n imam and: ,4 11 ,-3,, mo. scream 44 This invention relates to-a milltiphasesynchronous motor having a'rotor and 'a: stator, one ofvvhich; is .wou'nd*tordduce'a rotating or oscillating magnetic eld. "The windings aredistributedlto provide arr-even numberoffield pblesdistiibutedzovcr artio l of a circle tofprdduce equallyspacedi ld poles in an arc with anrfl'ectivenentralpolar'space betweenthe ends ofithe arc. Theother inem ber comprises an dddnumbercfsalient' pbles spaced at equal angles; one-ordain ddd inumber of salient p'oles' lyingivithinihe neutral pblar space and the remainder of the'siilientpoles being equal in number to Etheifibld ,pbles. The :ultimate ob ject of'jthis -invention isrto providela synchronousmotorwyhdch Wilh rtate at a speed proportional tothfrequency of the alternatipgvcumentdivided an-odd number. 'Heretofore synchronouszmotors havebeen constructed with an even number bfipoles 'in both stator arid arotor;'thefibldpolesbeing equally spaced. Theresiflt isthat a speed-6f rotation of the rotor is attainediequhl tq'the frequency di ided by [an eyent nu'mber. In

some instances, "it isdesirhble to bbtainga speed .of;=r'otation with, a 'givenffrequency which is intermediate successive Adjacent speeds attainable such motors. 'Asillustrative oi a-especific case; motionpi'cturegand sound-recordingzequipment have beeniouxid to,give :best results with a speed er; twenty four picture frames per second orninety feet of film passing perminute. "The shutter'shaft for such speed should, be 1940 revolutions per end which is a frequency commonly av'ail'nble from power supply;ilines,,'the ordinary synchronous motor-1 is operable with four poles at 1800 revblutions perfi inilwfand within poles at 1200 revolutions per minutefifThe desired speed of H40 revolutions; minnte is intermediate, and could begattained with five p'olesfiThe present practice is toemplovgearing tqproduceTthe'desii-ed speed. As is well known gearing is obj eetionable because of noise and because'it isextra; mechanism. My

motor has been'develpped to produce in 'eflect aiflfive p'o synchronous-moto W feby'ith shutt rshaft may b 'fliredtly; drive f fmme a s nchronous-motoroperating on sixty cycles. owever,' it will be 'obvious'from the subff-joined ,specification that with other fre- --quen'cie's' and other pole numbers; a variety of speeds maybe; attained-not now available inilfi up synchronous motors.

"Thebbjectsofithis invention are to provide ea motor structure having; the before men- 'tioned anddesired afeatures.

"These objectstogether with other objects L190 I and corresponding; accomplishments are obftained" by ineans of the embodimentof'my -in-' vention illustrated in {the accompanying Q- dravviBgs, irr-whichs- 1' is a side elevation partly in section I a stator lamination; and a rotor-lamination in F motor assembled relation, conductors in 'the stator slotsbeing ;indicate'd by small circles and'Fig; 4-is a vviringdiagram of the stator -;shown' indeVBIopedfform'.

"Referring to the particular construction? sh0wn,.the stator marked A compriseslaminations 5-,heldin assembled relationby end rings 6'and7. :CAbell housingj=8 is mounted over the laminations and isprovided witha hub 9 ,in' which is mounted a bearing 1' ournal 10. The bearing journal 10 is hollow and has a threaded' end.

The rotor-'Bpcomprises a bearing hub 11 rotatably mounted on hearing journal 10 and 10. Secured by a press fit to hub ll is a ring 13 having an" annular offset 14,; to receive a plate 15. The latter isvsecured to "the motor shaft'lfi which; is' journalled -in-member -'10. Built u onring '13. are rotor disposed between end plates;18,and 19.

"The stator is provided with slotsQO, there being" twenty "four slots showndistributed equally along an arc of two hundredel'ghty eight degrees or four fifths of alcircle. The

remaining are of the *circlecomprises seventy two'degrees or one fifth of'the circle. yIt is cut away, as best shown inFig; 3 and denoted by 21 so as to provide a relative long air gap.

Afthnee-pha'se distributed-- winding is laid in 3 held in place bya nut 12 threaded on journal minute. At si frequencybfwpycles perseclaminat-ions -'17" '-."having reached synchronousspeed'operates as slots 20 as indicated in Fig. 4. The neutral space at 21 forms a gap in the spacing of the windings so that a rotating magnetic field in efiect jumps 7 the gap. Geometrically the stator has five poles, but magnetically, one of these is neutral. V A o r The rotor B has, five salientgp oles, each marked 22. These poles are slotted as indicated by 23 to receive bars 24 turned over and electrically connected w endrings 18 and 19 and forming a squirrel cage induction motor rotor.

salient poles {of the rotor are angularly equal spaced with relation to the field. poles of the stator. V V i The motor after having been started and a synchronous motor. The-field flux. indicated: conventionally by the ellipses in Fig. 3 and marked F, travel geometrically two hundred eighty eight degrees and continue progressive movementwithout lapse oftime from theiarcuate beginning ofthe windings, delet-j ing a time interval in: the three .hundred'and.

sixty degrees of the stator equal to the angu lar extent of one field. pole. During the lltime required'for thee-field to traverse. the

stator, the rotor turns geometrically two hundredgandjeighty eight degrees and the deleted.

' fieldpole space is traversed in the same time interval as the-active fieldpole spaces The magnetic field moves efieictively through three =the speed of the rotor hundred sixty degrees, while the rotors travel through two-hundred eighty eight degrees,

for a salient polemust physically travel over the neutral or inactive polar space. Thus,

stator winding Q The enlarged 1r gap neutral position between stator and rotor.

1f the flux were permitted topass, it would set upafield which would oscillate back and. forth along the neutral gap, thereby super-lvv imposing on the rotor an oscillating mag netic field. This would superimpose a physical oscillation-on the rotorcause noise and develop heat due to eddy current and hysteresis losses. Theenlarged air gas reduces thisto an lnappreciable amount. i

It will be apparent that any suitable type of 5 stator winding may be. employed, and the: number of windings varied. It is 5 also ob-1 V vious. that the inductionmotor bars or their V equivalent in the rotor are not pertinent to the.

invention. i

What I-claim is 1. A synchronous motor havinga rotor member and a stator member, windings on.

one of said ,members-to produce a magnetic spaced alongan excitation arc ,at -equal an: gles, the remaining are of the'circle being is that of a five pole at d is provided v to; impede magnetic flux from passing atthis unwound and constituting a neutral arc, the other member having salient poles equally spaced about a circle at angles equal to the angles between said field poles.

2. A synchronous motor having a rotor 7 v I .equal angularly to an odd number of field These bars form no part of the present invention and are merely for thejpurp'ose of, providing starting means for the. motor." The poles," the other member having salient poles equally spaced about acircle at angles equal to the angles between-said field poles.

3..A- synchronousmotor having a;rotor gularly spaced equally along an excitation arc, the-remaining arc of the circle being equal toithelangle between adjacent field poles, the other. member having salient poles number-than said field poles.

LA synchronousj motor having a rotor anda. stator, windings onisaidstator to pro-- duce a magneticrfieldwith an even number of field poles spaced along an excitation arc at equal angles, the remainingarc of, the circle being equal angularly to an'odd number of field poles, the rotor having salient poles equally spacedabout a circleat anglesequal .to the angles between said field poles.

5. A synchronousmotor having a rotor member andla stator member, windings on gularly equal to the angle between adjacent field poles, the other member having salient poles equally: spaced ina circle and one greater. in numberthan said fieldpoles.

56.1Av synchronous 'motor havinga rotor member and a stator member, windings on one of said membersto. produce a magnetlc equally spacedin a circle and one greaterin field with an even;'number of field poles spaced. along an excitation arc. at equal angles, the {remaining are ;of the circle being equal angularly to an odd number of field polesythe other memberfhaving salient poles equally spaced about a circle at angles equal tothe angles between said field poles, the air gap between saidjmembers being uniform over the excitation arc and of greater magnitude over sald remaining are.

.7 A "ynchronouslmotor havinga rotormember and a, stator member, windings on oneof-said member-s te produce a magnetic field with an even number of fieldpoles angularly spaced equally along an excitation arc, the; remaining arc of thecircle-being equal, to the angle between adjacent field poles, the other member having salient poles equally spaced in a unclean-done greater in V number than said field poles, the air gap between said members being uniform over the excitation arc and of greater magnitude over said remaining arc.

8. A synchronous motor having a rotor member and a stator member, windings on one of said members to produce a magnetic field with four field poles spaced along an excitation are at equal angles, the remaining arc of the circle constituting a neutral are being equal angularly to one field pole, the other member having five salient poles equally spaced about a circle.

9. A synchronous motor having a rotor member and a stator member, windings on one of said members to produce a magnetic field with four field poles angularly spaced equally along an excitation arc, the remaining arc of the circle constituting a neutral are equal angularly to one field pole, the other member havin five salient poles equally spaced in a circ e, the air gap between said members being uniform over the excitation are and of greater magnitude over the remaining are.

10. A synchronous motor having a rotor and a stator, windings on'said members to produce a magnetic field with four field poles spaced along an excitation arc at equal angles, the remaining are of the circle constituting a neutral arc and being equal angularly to one field pole, the rotor having five salient poles equally spaced about a circle, the air gap between said rotor and stator being uniorm over the excitation arc and of greater magnitude over said neutral arc.

11. A synchronous motor having a rotor and a stator, windings on said stator to produce a magnetic field with four field poles angularly spaced equally along an excitation are, the remaining are of the circle constituting a neutral arc and being equal angularly to one field pole, the rotor having five salient poles equally spaced in a circle, the air gap between said rotor and stator being uniform over the excitation arc and of greater magnitude and uniform 'over said neutral arc.

In witness that I claim the foregoing I have hereunto subscribed my name this 23d day of April, 1930.

' OTIS C. MARTIN. 

